Paper 10: Estimation of Area, Yield and Production of Root and Tuber Crops in Thailand

Estimation par surface cultivée du rendement et de la production des cultures sarclées en Thaïlande

By
M. Chalit Amnuay

Center for Agricultural Information, Office of Agricultural Economics
Ministry of Agriculture and Co-operatives
Bangkok, Thailand
www.oae.go.th

Summary

The cassava production survey is a routine activity of the Office of Agricultural Economics (OAE), Ministry of Agriculture and Cooperatives. The information collected is used as a basis for formulating agricultural policy and planning. The survey is carried out at the national scale using sample survey techniques. It usually employs a stratified two-stage sample in which the villages are the primary sampling unit (psu) and the households are the ultimately sampling unit (usu). The data collection is done by OAE staff in each agro-economic zone through interview of the selected farmers in the sample. The data processing carried out at the central office.

The main problems encountered in the survey are lack of timeliness and under-estimation. A further problem is for instance the use of a fairly complicated questionnaire which makes it difficult for farmers to respond accurately. OAE has planned to change the data processing procedures, which now will be carried out in the field offices using notebook PC's in order to facilitate making the provincial estimates.

Résumé

L'enquête sur la culture du manioc est une activité de routine menée par le Bureau d'économie agricole (OAE) du ministère de l'Agriculture et des Coopératives. L'information recueillie est utilisée pour la formulation de la politique et de la planification agricoles. Cette enquête, réalisée à l'échelon national, fait appel à la technique d'enquête par sondage et principalement à l'échantillonnage stratifié en deux étapes. Les villages constituent l'unité d'échantillonnage primaire et les ménages l'unité d'échantillonnage finale. Le personnel de terrain de l'OAE collecte les données en interrogeant les agriculteurs témoins, le Bureau central se chargeant du traitement des données.

Le manque de ponctualité et la sous-estimation sont les principaux problèmes rencontrés. On a également constaté que les agriculteurs avaient du mal à répondre avec précision au questionnaire. L'OAE a l'intention de faire réaliser le traitement des données par les bureaux extérieurs en utilisant des ordinateurs portables pour obtenir les estimations provinciales.

Estimation of Area Yield and Production of Root and Tuber Crops in Thailand

Presented
by
Mr. Chalit Amnuay

Center for Agricultural Information, Office of Agricultural Economics
Ministry of Agriculture and Co-operatives
Bangkok, Thailand
www.oae.go.th

1. INTRODUCTION

Thailand is a tropical country located in Southeast Asia which extends from 6ð to 20ð north latitude and stretches from 97ð to 106ð east longitude with a total area of 514,000 square kilometers or about 51 million hectares. The total population is about 63 millions. It shares a border with Myanmar and the Lao PDR to the north, Cambodia and Lao PDR to the east, Myanmar and the Indian Ocean to the west and Malaysia and the Gulf of Thailand to the south. The Kingdom of Thailand is divided into four geographic regions: Northern, Northeastern, Central, and Southern and is subdivided into 76 administrative units called “Changwad” or province. Each Changwad is further divided into several Amphoes or districts and each Amphoe is subdivided into Tambon or communes. Each Tambon consists of about 5 - 10 Mubans or villages. In 2002, there are 789 Amphoes (including sub-districts), 7,061 Tambons and 65,310 Mubans in the country. The community area is also divided into three different types of municipalities: Nakorn or City, Muang or town, and Tambon or commune, depending on the population density. Other area of the province not covered by municipality is called non-municipal area and is considered as rural area. The non-municipal area is further divided into sanitary and non-sanitary areas.

Most of the civil service officers in each province are appointed by their respective departments from the central offices and work under the control and supervision of the governor, who is appointed by the Ministry of Interior. The officer in charge of each district is also appointed from the staff within the Ministry of Interior.

However, the chief of commune and the head of village are elected from the local people in that village. For certain departments, although the officers are assigned by their respective departments to work regularly in the province, they are officially independent from the governor control.

As regards the national economy, Thailand is predominantly an agricultural country. Approximately two-thirds of the population are engaged in agriculture. About 20 percent of the gross domestic product is derived from agricultural sector. Although agricultural exports share of the total export has been decreasing in recent years. The value of agricultural exports itself is increasing every year and is still a major source of export earning. Currently it constitutes about 35 percent of the total export value. For many years, The agricultural economy of Thailand was dominated by only one crop, rice.

After the World War II, crop diversification occurred in almost all regions of the country. Presently, Thailand's major crops are rice, corn, cassava, kenaf, sugarcane, beans, rubber, oil palm and fruit. Recently, fisheries products become more and more important source of export earning. However, other sectors such as manufacturing sector, wholesale and retail trade sector have also been increasingly important to the country economy every year.

As the country is moving towards more development, the demand for more detailed statistics and more commodities are also increasing. Besides the traditional important crops statistics as used to collect in the past, the statistics on minor crops which may have some potential for further expansion or investment are also needed. The purpose of this paper is to describe the existing statistical activities and methods used for collecting statistics on minor crops in Thailand and recommend an appropriate procedure for improving these statistics.

2. STATISTICAL ORGANIZATIONS

The statistical system of Thailand is a decentralized system. Each ministry has its own statistical unit to collect statistics to serve its own needs either through the survey method or as by product of administration. The principle agencies involved in food and agricultural and fisheries statistics/information are:

2.1 National Statistical Office (NSO)

The NSO is one of the department under the Office of the Prime Minister responsible for conducting all censuses relating to population, agriculture and fisheries, industry and many large-scale surveys not directly pertaining to agriculture such as labor force survey, and household socio-economic survey. Prior to 1975 the NSO had also conducted the nationwide crop surveys annually covering rice, corn and kenaf. The agricultural production surveys were later transferred to the Ministry of Agriculture and Cooperatives. Administratively, the NSO has branch offices in every province.

2.2 Office of Agricultural Economics (OAE)

The Office of Agricultural Economics, a departmental agency under Ministry of Agriculture and Cooperatives (MOAC), is the prime office responsible for collection, compilation, and dissemination of all current agricultural statistics. Other major functions of the OAE, besides the agricultural data collection activity, are conducting agricultural economic researches, formulating and recommending appropriate agricultural policies and development plan as well as monitoring and evaluating certain projects of the Ministry. Currently, there are about 684 permanent employees and officials in the OAE of which about 200 persons are attached in agro-economic zone offices. For Center for Agricultural Information (CAI), there are about 113 permanent staff, all of which station at the central office in Bangkok. As for agricultural surveys, the survey design, questionnaire design, survey manual preparation, data processing, and training of involved survey personnel are under the responsibility of CAI while the field works are managed by the zone staff. In every survey conducted by the CAI, the data collection is done by staff of the office zone (Agro-economic zone). A zone is a group of 2-4 provinces that is homogenous in terms of climatic, economic, and agricultural activities. Thus the data collected is then reported to the CAI, where it is rapidly tabulated by computer. After processing and analyzing, the result, are then compared with previous statistics, reference or information, and then put into a format for widely and easily use. To facilitate data users, CAI also compiles relevant agricultural statistics from other agencies and publishes in the Agricultural Statistics Yearbook as well as stores it in the database.

Current data collection activities of the OAE have been increasing every year especially after it has been promoted to be department status in 1979. The major surveys of OAE include crop and livestock surveys, socio-economic of agricultural household survey and cost of production survey. For crops surveys, OAE annually conducts specific surveys for the following crops namely rice, maize, cassava, sugarcane, soy bean, mung bean, ground nut, sorghum, kenaf, cotton, pineapple, garlic, shallot, onion, potato, coffee, oil palm, pepper, para rubber, and other fruit crops such as rambutan, durian, guava, lime, mangosteen, longan, lichee. The data collected in the specific crop survey are planted and harvested areas and production, dates of planting and harvesting, amount of fertilizer applied, amount of varieties planted, monthly product sale, number of total trees crops and productive tree (for tree and fruit crops only).

The survey design employed in the crop surveys are mostly the stratified two-stage sampling. For each crop, all villages which reported having the crop under survey are stratified into 3-4 strata according to the reported crop acreage. The sample villages are randomly drawn from each stratum. About 10 crop growers in each sample village are selected randomly for interview. The estimate of the total and mean of characteristic under study are then obtained from this sample.

2.3 Other agencies

In addition to the above two agencies, following agencies of the MOAC are also compiling and publishing agricultural statistics.

1) Department of Agricultural Economics (DAE) compiles the statistics on area and production of various crops from the reports of its local officers. This agency has their own agricultural extension officers in every Tambon.

2) Department of Livestock Development (DLD) undertakes collection and publication of figures on number of animals raised and slaughtered, dying from epidemic diseases, vaccinated and number of beasts of burden (elephants, horses, mules and asses). These figures are compiled from the reports of its local officers stationed in every district.

3) Department of Fisheries (DOF) collects and publishes all fisheries statistics. The Amphoe (District) Fisheries Office is the lowest administrative level of the DOF.

4) Royal Forest Department (RFD) keeps data on production and value of forestry production and number of sawmills in each province. Other published statistics are mostly administrative statistics relevant to its own activities.

In generally, cassava is planted is the wet season during May through August and having harvesting all the year Cassava,a drought-tolerant cash crop, contributes major income to farmers in the Northeast Cassava products are mainly exported as animal feed to the EU market, the largest buyer. Cassava roots, are processed in the farms of chips, pellets, flour and strach, and sago. About 90 % of cassava products for export is in the form pellets. The current cassava development is emphasized on varietal improvement rather than area expansion.

3. Statistical Methodology

3.1 Stratified Two-stage Random Sampling is used for the survey of each agricultural commodity. The villages, where surveyed crop is planted, is stratified into strata by using total planted area in the villages. Those information is obtained from agroeconomic zone office. The surveyor then lists all households, who plant surveyed crop, in the sample village. Sample households are then random selected and interviewed for data collection. In conclusion, Stratified Two-stage Random Sampling comprises 2 steps:

-Primary Sampling Unit (select village)

-Secondary Sampling Unit (select household)

Total estimation ()

Where by

=total estimation
y_hij=value of characteristic of household j from village i, stratum h
M_hi=number of households listed from village i, stratum h
m_hi=number of sample households of village i, stratum h
N_h=total number of village, stratum h
n_h=number of sample village, stratum h
h=1,2,3.................L
i=1,2,3...........n_h
j=1,2,3...........m_hi
M_hi/m_hi=expansion factor at primary sampling unit level
N_h/n_h=expansion factor at stratum level

Estimation of Variance []

(2)

where by

The root crops are cassava and potato, mostly were the stratified two-stage sampling the detail are as follows:

3.2 Frame construction:

Variables used for frame construction one planted area within village boundary, and classified in to 4 stratum:

Stratum 1: 0 - 100 hectares

Stratum 2: 101 - 500 hectares

Stratum 3: 501 - 1,000 hectares

Stratum 4: >1,000 hectares

3.3 Sample size

A proportional allocation has often been used in determining the number of sample villages in each stratum in each province. The number of sample villages depends on the number of villages within a stratum in a province. The total number of village samples have very often been constrained by budget, personal, vehicles and time. Generally the average sample village is 10 percent and sample household is 10-15 percent.

3.4 Data processing and dissemination

The data processing generally for the survey are generally computerized. Questionnaires are so designed that data entry can be done directly from the filled questionnaires. After the field work is completed the filled questionnaires are sent to central office for processing and analysis The survey result is submitted to the approval committee for considering the data before release to the general published such as newspaper, radio, TV including homepage. Currently each department of the MOAC has its own website. There are the name of some website for example: www.oae.go.th / www.doae.go.th /www.doa.go.th

Regarding publications, the result of each survey are published separately. At the and of each crop year, the agricultural statistics yearbook contained the survey results as well as secondary data collected by the OAE is also published. The information on production situation and marketing of agricultural products are published weekly in “The Production and Marketing of Agricultural Products News bulletin. About 6,500 copies are distributed. The agricultural economics situation is also reported in a monthly journal, “The Agricultural Economic News” About 4,500 copies are distributed monthly.

4. Future Plans

The MOAC is preparing to launch two major projects namely “The Mapping for Natural Resources and Ministry of Agriculture and Cooperatives Properties Administration Project” and “The Farmer Registration and Identification Card Project”. Although these two projects are not purposively designed for agricultural survey, the results of the projects will be very useful for improving of the agricultural survey methodology.

For the first project, the color aerial photo at scale 1:25,000 will be taken to cover the whole country within 1 - 2 years. Therefore, the area frame sapling technique can be adopted using the new color aerial photo. Infact, the area frame sampling used to be implemented unsucessfully in Thailand 15 years ago due to the use of very old aerial photo.

Under the second project, all farmers are required to register with the MOAC if they want to participate in certain government programs. The information obtained from this project will be very useful for conducting the agricultural survey. It is also interesting to note that the MOAC is currentlly establish the Tambon Technology Transfer Center (TTTC), one center for each province, as a pilot project. This center is designed to be the “one - stop service” center for the farmers in that Tambon (sub - district). One of the major function of the center is to the information center for the farmers in the area. The relevant information such as technology and marketing information will be distributed to farmers through this center. If successful, the TTTC will be expanded to cover every Tambon in the country.

5. Problems and Constraints

5.1 Normally,the number of samples is too small due to a large number of commodities to be surveyed and disseminated as the number of samples is assigned in accordance with allocated budget, available manpower, and vehicle. This causes high fluctuation and inaccuracy of the survey results of some commodities.

5.2 The problem in conducting the survey is that there are so many items to be collected. This involved a lot of time and effort to do the field work. Moreover, many experienced enumerators or interviewers are required. The timing and frequency of the survey is also very important. About two to three visits per season seem to be appropriate in getting the correct answer from the farmers.

5.3 At present most of actual agricultural statistics or survey data are released later than 6-8 months after the reference period. So that most of user make choice to used another source of information

5.4 Due to a limitation for lacking of data especially such as change in stocks or existing stocks, which is very essential for balance sheet. Farm book - keeping technique may be an alternative method for getting the production estimate.

5.5 In many situations we can find auxillary or ancillary data for improving the estimates, that is ratio estimator.

(follows the 3 tables presented)

Table 1: Cassava - Planted Area, Harvested Area and Production

Table 2: Potato - Planted Area, Harvested Area and Production

Table 3: Percentage of Monthly Production of Cassava and Potato